1. Technical Field
This invention generally relates to a scroll compressor with a scroll compression mechanism made up of a fixed scroll and a moving scroll and more specifically to technology to prevent damage to the scroll compression mechanism due to opposite rotation of the moving scroll to the correct rotation direction.
2. Background Art
A typical scroll compressor of this type has in a casing a scroll compression mechanism comprising two different scrolls, namely a moving scroll rotatably driven by a motor and a fixed scroll secured to the casing. The moving scroll has a panel board from which an involute body projects. On the other hand, the fixed scroll has a panel board disposed so as to face the panel board of the moving scroll. Disposed on the panel board of the fixed scroll is an involute body which engages with the involute body of the moving scroll in order that a compression chamber may be defined therebetween. Approximately centrally formed in the panel board of the fixed scroll is a discharge port through which gas compressed in a compression chamber between the two involute bodies is discharged towards the back of the fixed scroll. A portion of the casing on the side of the back of the fixed scroll acts as a high-pressure discharge chamber, in other words, the casing is divided into two portions, namely the high-pressure discharge chamber and a low-pressure suction chamber. If such division of the casing internal cavity is made by the fixed scroll per se, the fixed scroll is likely to undergo bending due to differential in pressure between the discharge chamber and the suction chamber. As a result, the compressor falls off in performance. With a view to providing a solution to such a problem, Japanese Patent Application Laying Open Gazette No. 2-125986 has offered a proposal in which a barrier wall (partition) for providing a division into a discharge chamber and a suction chamber is disposed on the fixed scroll rear side.
Japanese Patent Application Laying Open Gazette No. 4-241702 shows a scroll compressor. A discharge opening is formed in the barrier wall for introducing gas, discharged from the discharge port of the fixed scroll, to the discharge chamber. A check valve is disposed at an opening portion of the discharge opening on the side of the discharge chamber, in order to prevent reverse flow of the gas from the discharge chamber into the suction chamber. In accordance with this prior art scroll compressor, a seal member is provided between the fixed scroll and the barrier wall in order to provide a hermetical seal between an inner compartment including the discharge port and the discharge opening and an outer compartment on the peripheral side of a space defined between the fixed scroll and the barrier wall.
In such a scroll compressor, when the moving scroll is normally operated, that is, when the moving scroll is operated in the correct rotation direction, gas flows in the scroll compression mechanism. Frictional heat, caused by contact of the forward end surfaces of the involute bodies of the fixed and moving scrolls with their respectively facing panel boards, is released to outside the scroll compression mechanism because of such a gas flow, therefore producing no problems.
If the moving scroll is opposition operated or operated in a rotation direction opposite to the correct rotation direction for some reason such as inaccurate power wiring of the drive motor, then the check valve is closed. The discharge port pressure falls below that of the suction and discharge chambers, and a vacuum is finally created. Because of this, gas stagnates and ceases to flow and frictional heat becomes close in the scroll compression mechanism. Both of the involute bodies undergo thermal expansion due to the fictional heat, as a result of which the forward end surfaces of the involute bodies are abnormally pressed against their respectively facing panel boards. Much greater frictional heat is produced, therefore causing seizing in the forward end surfaces of the involute bodies immediately after the moving scroll starts rotating. There is room for improvement on the prior art technology.
Japanese Patent Application Laying Open Gazette No. 1-318778 offers a proposal. A relief passage is formed in the fixed scroll for providing connection between the periphery of the moving and fixed scrolls and the discharge port, and a relief valve is disposed which is operable to close the relief passage during the correct operation period while on the other hand opening the relief passage during the reverse operation period. During the reverse operation period, gas is circulated, through the relief passage, between the discharge and suction sides of the scroll compression mechanism, with a view to preventing damage to the involute bodies due to seizing. In this prior art technique, gas is circulated as follows. The gas is first forced to flow in a compression chamber of the scroll compression mechanism from the centrally located discharge port toward the periphery in a direction opposite to the direction of the correct operation period. Thereafter, the gas is forced to return to the discharge port by way of the relief passage. In this way, frictional heat generated is removed to outside the scroll compression mechanism.
In accordance with the technology proposed in JP Pat. Appln. Laying Open Gazette No. 1-318778, the involute body forward end surface will not undergo seizing as soon as the moving scroll starts rotating; however, since the relief passage is formed within the fixed scroll this becomes a bar to sufficient removal of frictional heat to outside the scroll compression mechanism. Eventually, the frictional heat causes damage to the involute bodies after an elapse of a certain period of time. This prior art technique may be problematic.
In addition to the above-noted problem, even when the relief passage is closed by the relief valve during the correct operation period, compressed gas will go into the relief passage. The fixed scroll will become deformed and the loss of heating will occur. Further, due to reverse flow of the gas that entered the relief passage, the gas reexpands resulting in a drop in the compressor performance.
Bearing in mind the foregoing problems with prior art techniques, the present invention was made. Accordingly, a general object of this invention is to provide technology having the ability to effectively prevent the occurrence of involute body forward end surface seizing. This object is achieved by improvements in scroll compressors with a barrier wall having a discharge opening and a check valve disposed on the side of a discharge chamber of a scroll compression mechanism, more specifically, by improvements in the construction of seal members to be disposed between the barrier wall and the fixed scroll, whereby frictional heat, occurring in the involute body forward end surfaces during the reverse operation period, is positively removed to outside the scroll compression mechanism, without a drop in the compressor performance during the correct operation period.